Means for regulating aspirated secondary air for exhaust gas conversion



March 1966 R. J. J. HAMBLIN ETAL 3,237,399

MEANS FOR REGULATING ASPIRATED SECONDARY AIR FOR EXHAUST GAS CONVERSION2 Sheets-Sheet 1 Filed Nov. 4, 1963 amt 2 5 5 Miles Per Hour- E quiv/anfCruise Road Load Figure 2 40 Miles Per Hour (Equivalent Cruise RoadLoad) Fig ure 3 K Secondary Air ln/af Movable Damper l enfuri FormAsp/'rafor Converter Exhaust Gas ln/ef IN VE N 7'0/?$-' Robert J. J.Hamb/in Frank V. Purse .4 TTOR/VEYS March 1966 R. J. J. HAMBLIN ETAL3,237,399

MEANS FOR REGULATING ASPIRATED SECONDARY AIR FOR EXHAUST GAS CONVERSIONFiled Nov. 4, 1963 2 Sheets-Sheet 2 Figure 4 Figure 4a I 33 L l r (E I35 x j :j: 28 //v vs/v rams- Robert J. J. Hamb/in Fran/r V. PurseWilliam M. Shaffer mal conversion.

United States Patent 3 237,399 MEANS FOR REGULXTING ASPIRATED SECOND-ARY AIR FOR EXHAUST GAS CONVERSION Robert J. J. Hamblin, Chicago, FrankV. Purse, Northfield, and William M. Sheffer, Park Forest, 11].,assignors to Universal Oil Products Company, Des Plaines, Ill., acorporation of Delaware Filed Nov. 4, 1963, Ser. No. 321,271 3 Claims.(CI. 60-30) The present invention is directed to means for regulatingaspirated secondary air and more particularly to the control ofsecondary air being admixed with engine exhaust gases for introductioninto a converter for the oxidation of the combustible contaminants insaid gases.

Various types of devices have been utilized to supply secondary air;however, most devices have operated to increase air flow along withincreasing exhaust gas flows and not to decrease the proportion ofaspiration responsive to motor speed or to the rate of flow of theexhaust gas stream. Inasmuch as excessive secondary air will have achilling effect upon the reactant streams and the catalyst bed of acatalytic converter or upon the thermal reaction in a thermal reactor,the present invention provides means for reducing the supply ofaspirated secondary air as the primary gas rate reaches a predeterminedvalue.

The removal of certain components from vehicular exhaust gases is deemedto be of importance at the present time. The unavoidably incompletecombustion of hydro carbon fuels by the gasoline or diesel engineresults in the generation of substantial amounts of unburnedhydrocarbons and other undesirable waste gases which are discharged tothe atmosphere through the exhaust line. With the ever-increasingconcentration of automobiles, particularly in urban areas, the resultantdischarge of these undesirable products into the atmosphere may reachhigh proportions. These combustion products are known to react withatmospheric oxygen under the influence of sunlight to produce smog. Suchwaste gases include, for example, saturated and unsaturatedhydrocarbons, carbon monoxide, aromatics, partially oxidizedhydrocarbons such as alcohols, ketones, aldehydes and acids, and oxidesof nitrogen and sulfur.

Methods for converting vehicular exhaust gases to harmless materials,such as, for example, carbon dioxide and water may be classified intotwo broad areas:

(1) catalytic conversion and 2) non-catalytic or ther- In the catalyticmethod, the exhaust gases leaving the engine are passed, with or withoutheating or cooling, into contact with a suitable conversion catalyst andthe conversion products of the resulting reactions are thence dischargedinto the atmosphere. In general, the preferred conversion react-ionsinvolve more or less complete oxidation of combustibles, and to this endit is necessary to provide sufiicient oxygen, obtained from air or otheroxygen-containing gas, in the exhaust gases prior to contact with thecatalyst. In the thermal method, the exhaust gases are simply heated to,or maintained at, a sufficient-ly high temperature, in the presence ofoxygen so as to burn combustibles without utilization of a catalyst.With either method, it is necessary to provide at least a stoichiometricamount, and preferably an excess amount, of oxygen or air in the exhaustgases. It is not feasible to manipulate the carburetor in order toprovide such excess air since this would seriously reduce the efiiciencyand/ or power of the engine, and, therefore, it is usually desirable toseparately add the required amount of air to the exhaust gases at apoint between the exhaust valve ports of the engine and the catalytic orthermal conversion zone located downstream therefrom. Such additionalair is also termed secondary air, as

opposed to the primary air injected by the carburetor and employed tosupport combustion of the fuel within the engine cylinders proper.

The amount of secondary air required for the efficient oxidation of theexhaust gases varies with engine operation. For example, reference tocurve A in the accompanying FIGURE 1 of the drawings illustratesdiagrammatically the amount of secondary air required for efficientoxidation in response to variations in engine operation. The percent ofair aspiration expressed in pounds of air per one hundred pounds ofexhaust gases is plotted against engine operation in equivalent cruiseroad load expressed in miles per hour. It is not intended that thiscurve, as well as the accompanying curves shown in the drawings, berepresentative of all engines or converter operations, but it doespresent graphically the typical secondary air requirements for theconversion of unburned components in an exhaust gas stream Within acatalytic type converter receiving such exhaust gases from a Ford 332cubic inch V8 automobile engine. The use of an uncontrolled secondaryair inlet into an aspirator in an exhaust gas line provides airinjection in a manner which may be shown to be in accordancediagrammatically with curve B of FIGURE 1 of the drawing. Here again, itmay be noted that the curve presented is merely representative of anaspirating operation utilizing an 1% diameter air inlet line to thediffuser section of a typical venturi-form aspirator fitted into thestandard exhaust gas line of a V8 automobile engine at a point ahead ofa catalytic gas converter. A comparison of the two curves shows that aconsiderable quantity of excess secondary air is being aspirated by highspeed engine operation and accompanying high gas flow rates. Thisexcessive secondary air has an undesired controlling effect on theexhaust gas stream and the converter, and affects pertormance in twodifferent ways. Firstly, the instantaneous conversion ability of thedevice is directly affected by operating temperature since the oxidationreaction rates increase more than proportionately as the absolutetemperature of the operation increases. Secondly, the net rate of theaccumulation of solid deposits, such as compounds of lead, having anadverse effect upon performance is decreased by an increase in operatingtemperature. In a catalytic unit, this high temperature eifec-t is mostpronounced in the upstream portion of the apparatus. The hightemperature removal of the deposits can preclude rapid deactivation inthe catalyst bed, while in the thermal devices, such deposits interferewith heat transfer rates in heat exchange sections of the apparatus.

The beneficial etfects of controlling the aspiration of secondary air isbest shown by reference to FIGURE 2 of the drawing; for example, curve Cindicates in a diagrammatic manner how a snap action type of damper orregulator will serve to decrease secondary air introduction at higherengine speeds. In other words, a resulting operation conforming to curveC will more closely approximate the desired introduction of secondaryair as illustrated in curve A of FIGURE 1. In still another type ofmechanical regulation, as provided by a throttling type of damper orvalve means, there may result a curve D type of operation which likewiseapproximates the regulation of aspirated secondary air in accordancewith the desired amounts as illustrated by the curve A. In all of thevarious mechanical embodiments providing the regulation of secondary airby the present invention, there is no complete shut off of the secondaryair at high speeds, but merely the reduction of the total quantity beingaspirated. The use of properly sized balancing means in turn provide theinitiation of the reduction in secondary air at predetermined enginespeeds or exhaust gas flow rates.

Various pumping means may be used to introduce air to a converter, butfor simplicity, a preferred means of adding secondary air is with a jetpump or aspirator serially connected in, or forming a part of, theexhaust gas pipe system and disposed upstream from the gas conversionzone. Jet pumps are well known in the art of fluid transport and only abrief description of the principal elements thereof is necessary here.In essence, a jet pump consists of an inlet nozzle arranged to dischargeinto a venturi-shaped diffuser section. The diffuser generally comprisesan inlet throat section having a crosssectionalarea smaller than the jetpump outlet and a gradually expanding outlet section to increase thecrosssectional area up to that of the jet pump outlet. A conduit orother port means for conducting the aspirated or injected fluid connectswith the interior ofthe diffuser at the zone of the nozzle openingandadjacent to the narrow portion of the venturi. A stream of motivefluid is passed through the nozzle and is thereby formed into a highvelocity jet which passes intothe diffuser and creates a region of lowpressure at the upstream end thereof, into which the aspirated fluid isentrained. The diffuser functions to mix the. motive fluid and theaspirated fluid and to convert some of the velocity head of the mixtureinto static head.

When aventuri-form aspirator is employed to inject air into an exhaustgas stream, the exhaust gas itself servesas the motive fluid, thesecondary air being the injected fluid; thus, when aspirator means isapplied to the exhaust gas stream of an internal combustion engine,especially a spark ignition engine operated under Widely varyingconditions of speed and loadas in the case of a motor vehicle, peculiardifliculties are thereby encountered. The ordinary operation of a motorvehicle is customarily divided into four modes; namely, the modes ofidle, acceleration, cruise anddeceleration. At idle and deceleration,most spark ignition engines operate with a richer fuel-air ratio thanduring the open throttle operation of acceleration and cruise, and theconcentration of combustibles in the exhaust gases is very much higherthan during cruise and acceleration. The secondary air requirements forsatisfactory conversion of the exhaust gas are hence larger, relative toexhaust gas flow, at such rich mixture, low engine speed operation; inother words, the mass ratio of secondary air aspirated to exhaust gasmust be greater at low engine speed, and consequently at low exhaust gasflow, than at high engine speed, correspending to high exhaust gas flow.

It is a principal object of the present invention to utilize a movabledamper member in combination with an air inlet means to a venturi-formaspirator such that at high speeds for exhaust gas rates there is apartial blockage on the air flow through the inlet line.

It is a further object of the present invention to utilize a balancingmeans, which may be of the spring or counterweight type, in a simple,trouble-free arrangement in combination with the damper means so as topreclude frequent repairs or need for inspection.

In a broad aspect, the present invention provides in combination with anexhaust gas converter and a venturifor-m aspirating means forintroducing a mixed exhaust gas and air flow through said converter, animproved air inlet regulating means which comprises in combination, anopen-ended air inlet conduit connective with the throat portion of saidventuri-form aspirating nozzle, a movable normally open damper memberpositioned across said air inlet conduit, and a load balacing meansconnecting to said damper member, with said damper member placed andbalanced with said balancing means to have a substantially fully openposition and alternatively a partially blocking position across said airinlet conduit, and with the movement between such positions beingresponsive to the suction on said air inlet conduit, which varies withthe exhaust gas flow rate through said aspirating nozzle.

In a somewhat more specific embodiment, the present invention providesflow regulation means for the air inlet conduit to a venturi-formaspirator, which comprises in combination, a movable damper member inthe form of a rotatable mounted plate positioned internally within theair inlet conduit, with said plate mounted on a rotatable shaft memberand being sized smaller than the interior of said air inlet conduit toprovide a predetermined space therebetween, said plate further having acurved aerofoil edge extending parallel to the shaft memher, and saidshaft member having at least one end portion extending through the wallof the conduit means and connecting to counterweight means, saidcounterweight means being angularly positioned to hold the pivotallymounted plate in a normally open position for low flow rates through theinlet conduit.

In still another movable plate embodiment, the movable damper member maycomprise a plate section hingedly connected and positioned across theendportion of the air inlet conduit to the diifuser' section of theventuri-form aspirator andsuitable counterweight means connected to thehinged plate whereby there may be pulling in of the plate member to seatagainst the end ofthe conduit and a partial blocking of the inlet end ofthe air inlet conduit responsive to the gas flow rate through theve-nturi and a predetermined rate of air flow through the end of theconduit.

It is not intended to limit the operation and movement of a dampermember toany one form of counterweight means inasmuch as special formsof tension or compression springs as well as adjustable and movableweight means on various types of lever arms may provide the desiredbalancing effect for the positioning of the damper plate means. The useof pi-votally or hin-gedly mounted damper plate members connecting withthe balancing means are normally operative to provide a form of snapaction in block or unblocking .the air flow through an inlet conduit.However, a throttling action may be pro-. vided by the use of balancingmeans which hold the damper member in a normally open position for lowflow rates but Will permit closure or full blocking effect responsive toincreasing air flow rates around or through a particular damper member.Such balancing means may be either counterweight means or spring means.For example, a damper member may be urged into initiating the closure atgas flow rates corresponding to engine op-- eration equivalents of from30 to 35 miles per hour and;

a completion of the blocking by the damper member effective at 351 to 45miles per hour. How-everm, it should benoted that suitable springbalancing means or counter-- Weight means may also be utilized toinitiate closure of the primary gas flow rate which may correspond tofrom. 10 mph. to 50 mph. and completed at rates correspond-- i-ng to 20to 60 mph. The amount of blocking that is: effected by the movabledamper member itself may also vary and generally the regulatingapparatus will provide: for an unblocked flow or residual open area of 5to 10 percent of the cross sectional area of the inlet line such thatthere will always be some aspiration of secondary air atv high enginespeeds.

Reference to the accompanying drawings of various flow regulating meanswill serve to further amplify the improved designs and arrangementsunder the scope of the present invention in providing movable andadjust: able damper means which will move responsive to air aspirationrates.

FIGURE 3 of the drawing indicates diagrammatically the use of aventuri-form aspirator upstream from an exhaust gas converter to effectthe suction and mixing of secondary air with the exhaust gas stream.

FIGURE 4 of the drawing indicates one form of movable butterfly type ofmovable damper member on a rotating shaft mounting within an air inletconduit.

FIGURE 4(a) indicates a modification in the balancing of the dampermember by the use of a spiral form of coil spring.

FIGURE 5 of the drawing indicates diagrammatically a hinge mountinghaving a movable damper member which is spring balanced and operative topartially block air inlet flow directly at the end of the secondary airinlet conduit.

FIGURE 6 of the drawing is a sectional elevational view of one form ofmovable damper member which provides throttling action in effecting thegradual blocking of aspirated secondary air responsive to air flow ratesthrough and around the damper member.

FIGURE 7 of the drawing also indicates in a sectional elevational view amodified form of movable throttling type of damper member which closesagainst a compression spring that urges the member into a normally openposition.

Referring now particularly to FIGURE 3 of the drawing, there is shown anexhaust gas inlet line 1 which receives exhaust gases from an engine,not shown, and in turn passes such exhaust gases through a nozzle 2 intoa venturi-form aspirator 3 and subsequently through line 4 to acatalytic converter indicated diagrammatically as 5. Secondary air tosustain the catalytic oxidation of combustibles in the exhaust gasstream is drawn into the diffuser section of the venturi-form aspirator3 by way of inlet 6 and air inlet conduit 7. The latter has an open endportion 8 with a movable damper member 9 operative to effect partialblocking of the internal area of inlet section 8 responsive to air flowthrough the conduit and differential pressure across the damper plate.Damper member 9 is indicated diagrammatically as connective with acounterweight member 10 which holds the damper in a normally openposition for low gas flow rates but can be raised responsive to movementof the damper member 9 under the influence of high air flow rates intothe end portion 8. Increased air flow is in turn responsive to the rateof exhaust gas flow through aspirator 3 and the resulting suction on theair inlet conduits 6 and 7. As will be pointed out more fullyhereinafter, various forms of movable damper means may be provided incombination with the air inlet conduit; however, the arrangement ofFIGURE 3 shows diagrammatically the use of air regulating means incombination with an aspirated air inlet for a venturi-form aspiratorwhich in turn is used in combination with an engine exhaust gas lineproviding a mixture of exhaust gases and secondary air to an exhaust gasconverter means. The converter 5 is indicated as being of a catalyticform in the present embodiment but, here, again, it may be pointed outthat an exhaust gas oxidizing unit may be of the after burner typeutilizing high temperature thermal oxidation of the combustibles in theexhaust gas stream. Furthermore, the damper may be located at anyconvenient point in air conduit 7.

Referring now more particularly to FIGURE 4 of the drawing, there isindicated a substantially square or rectangular form of air inletconduit 11 which is connective with a venturi-form aspirator, not shown.Rotatably mounted internally within the portion 11 is a substantiallysquare or rectangular form of damper plate member 12 mounted on a rod orshaft member 13- which has end portions that extend through side wallsof the end conduit section 11. The damper plate member 12 may beremovably attached to the shaft member 13 by screw members 14, oralternatively, there may be a fixed riveted or welded connection betweenthe two members. One end of the shaft 13 has an extended lever armportion 15 and at least one threadedly attached weight member 16 suchthat there is a counterweight action provided to position and balancethe damper member 12 in a desired position within the end portion 11.Also, in accordance with the present invention, the lever arm 15 extendssubstantially at right angles from the shaft member 13 and at a smallangle 0 with respect to the perpendicular to the plane of the damperplate 12 such that when the weight 16 holds the counterweight arm 15 ina depending position against the stop 19, the damper plate will be in anormally open substantially horizontal plane. Of course, where thedamper member is mounted in a conduit section which is not horizontal,then the balancing arm will be arranged at an acute angle with respectto the plane of the damper to properly hold it at a normally openposition with respect to the angle of the conduit.

A preferred design for the damper plate 12 provides a curved aero-foiledge 17 across the upstream end portion thereof such that a slightcurved surface continuously faces the incoming air inlet stream. Thisdesign permits an increasing flow rate of secondary air to increasepressure against the end of the damper plate memher and gradually urgeit downwardly against the action of the counterweight 16 on level arm 15until at high flow rates above a predetermined engine speed, there willbe a substantially vertical positioning for the damper plate member 12and a substantially horizontal positioning of lever arm 15 and itsweight 16. The positioning of a plate member 12 in a vertical planeeffects a partial blocking of the air flow to the inlet conduitpermitting only that flow which is around the periphery of the dampermember or which may be provided through the damper member byperforations. Generally, a preferred design provides an approximate ofblocking air flow such that the remaining open space will permit aresulting residual aspiration for high speed engine operations. Thepresent form of butterfly type of member having the counterweight meansand the aerofoil edge can effect a relatively fast snap action type ofoperation or a slower throttling type of operation. The action dependsupon the shape of the aerofoil section of the plate member, the amountof off-center mounting of the plate with respect to the rotating shaftmember 13, the weight and angle of the balancing arm 15 and weight 16.Upper and lower stop members, such as 18 and 19, are shown being mountedon the side wall of the inlet section 11 to provide limits for themovement of the balance arm 15; however, generally, the movement of sucharm 15 will be limited to approximately of rotation by the action of thegravity loading from weight 16 causing the damper plate 12 to be in anormally open position, and alternatively the effect of the differentialpressure caused by the atmospheric pressure on the upstream end of theplate and the decreased downstream pressure produced by high aspirationholding the plate member 12 in a substantially vertical plane.

In a variation of the movable damper member construction, there is shownin FIGURE 4a of the drawing the use of a coil spring 16a connectingbetween a shaft arm 15a and a stop 18a. Thus, the damper member 12a inconduit section 11a works against the spring 16a as a balancing member,with the latter supplying a restoring force to hold the damper in anormally open position in the conduit for low flow rates. In thisembodiment, the angle of the conduit is not dependent upon a gravityacting counterweight and is not critical.

The counterweight may also be incorporated into the trailing edge of thedamper plate and the stops 18 and 19 made internal. In such anembodiment the duct or conduit will be mounted at a suitable angle tothe horizontal to have the damper in normally open position for lowaspiration rates. Also, in the embodiment of the apparatus of FIGURES 4and 4a the damper members may be adapted to conduit cross sections orshapes other than rectangular.

In the embodiment of FIGURE 5, there is shown an end portion of an airinlet conduit 20 having a damper plate 21 hingedly connecting to itsside by hinge means 22 whereby the open end of inlet conduit 20 may bepartially blocked as to the aspiration of secondary air. The connectionof the secondary air inlet conduit to the aspirating means is not shownin the present FIGURE 5 but would be in accordance with the arrangementshown in FIGURE 3 of the drawing. At low speed engine operations, thedamper plate member 21 is in a normally open position as shown by thedashed lines, being held in a raised position by a suitable tensionspring 23 extending between support member 24 and an eye member 25 whichis in turn positioned on plate member 21 to suit the rate and tension ofspring 23.

Damper plate member 21 may be sized somewhat smaller in width than theopen end portion of conduit 20, as shown in the drawing, oralternatively may be provided with sufiicient open slot means, such as26, to permit a desired percentage of air inlet flow even in the closedor blocked position. The operation of the present embodiment is similarto that of the movable plate in FIGURE 4 of the drawing, where anincreasing speed of engine operation will cause a greater exhaust gasflow through the venturi-forrn aspirator to in turn cause a sufiicientamount of suction on the secondary air inlet line to cause a pressuredifferential between the suction side of the movable plate 21 and theexternal atmospheric pressure to cause a closure of the plate member 21down against the open end of conduit 20. Generally, with the use ofcounterweight means or a tension spring, such as 23, for holding themovable plate member 21 in a normally open position for low enginespeeds, there will tend to be a critical speed of operation where thepressure differential will snap the movable damper member against theend of conduit 20 in the blocked position such that the operation, likethe embodiment of FIGURE 4, will be substantially in accordance with theoperation shown in curve C of FlGURE 2 of the drawing. On the otherhand, the choice of weight or gauge of the damper member 21, the size ofthe air inlet conduit 20, or in the type of tension spring utilized tohold the damper member in a raised position, there may be some degree ofthrottling action provided for the operation or closure of the dampermember 21 responsive to variations in the exhaust gas flow rate end andthe suction from the aspirator means. The present embodiment shows asingle centrally located slot 26, in addition to the aforementionedunblocked openings which ooccur between the edges of the damper platemember 21 and the circular periphery of the open end of conduit 20;however, it should be noted that the damper plate may be made in acircular configuration and additional slot means, such as 26, maybeprovided to furnish the desired open area through the damper memberwhereby at least some secondary air is aspirated through the inletconduit at high speed engine operations. It will be noted upon refernceto cuve A of FIGURE 2 that there is an increasing need of air for highspeed operations primarily because of the high speed fuel enrichmentarising from the usual carburetor construction having high speed jetmeans addition of fuel for high speed operations.

In FIGURE 6 of the drawing there is shown still another embodiment ofmovable damper means which is operative to decrease the proportionofsecondary air intake responsive to increasing exhaust gas flow rates. Anair inlet conduit 27 is provided with an enlarged damper holdingsect-ion 28 and an air inlet end 29. The interior of the enlargedsection 28 accommodates a compression spring 31 which in turn engagesand supports a hollow cylindrical form damper plug member 32. The latterhas a tapering downstream end portion adapted to engage and seat withina tapering seat section 30 at the upstream end of conduit 27. Theupstream end portion of the damper plug member 32 has a perforatetransverse plate section 33 that extends in a flangelike manner beyondthe exterior wall of the cylindrical portion 32 to provide a shoulderportion to in turn hold the end of compression spring 3-1. The latterthus holds the damper member in a normally open position away from theseat 30 for low air flow rates. The major portion of the exteriorperiphery of the transverse section 33 is, however, spaced inwardly fromthe inside wall of section- 28 such that air flow may pass in asubstantially annular flow around the damper member 32, from the intakesection 2 to the conduit section 27, as long as the spring member 21 isholding the damper plug 32 away from the seat 30. Spaced portions 34project from the periphery of the transverse plate section 33 to act asguide members within the inside wall of section 28. The presentembodiment indicates a single opening 35 within the central portion oftransverse plate 33, although a plurality of smaller openings may beutilized instead to be in conformance with the present invention toprovide a percentage of secondary aspiration at high speed operationseven though the damper member may be in the blocking position.

In the operation of the present embodiment, an increasing exhaust gasflow rate in turn provides a greater aspiration and suction from theventuri-form aspirator means to cause an increase in differentialpressure between the downstream side of the movable damper member 32 andthe external atmospheric air inlet side thereof, such that thedifferential pressure will gradually push against the compression spring21 to effect a fully blocking position at the downstream end of thedamper plug member 32 engaging the seat 30. Here again, the point atwhich the fully blocking position will be accomplished will depend uponvarious factors, including: the area of the transverse plate 33 withrespect to the inside diameter of the enlarged section 23, the type ofcompression spring 31, the size of the secondary air inlet conduit 27,the aspirator design, and the like. The present design, however, tendsto provide a throttling type of reduction in the secondary air intakeresponsive to increasing gas flow rates through the aspirator such thatthe type of operation is substantially in accordance with the curve D ofFIGURE 2 of the drawing. Full blocking by the damper member, permittingflow only through the central opening 35, may be accomplished at anypredetermined speed, equivalent to say 35 to 45 miles per hour vehicularspeed, although, of course, other modified designs and adjustments maybe made to provide the desired blocking at other predetermined speeds.

In FIGURE 7 of the drawing, there is shown still another embodiment ofmoveable damper means operative at the end of an air inlet conduit 35such that secondary air may be partially blocked as the exhaust gas flowrates increase. In this design, the very outer end of the air inletconduit 36 is partially curved to provide a seating surface 37 which inturn can engage a damper plug member 38 which has an outwardly flaringportion at the upstream end thereof. The flaring cylindrical form dampermember 38 is positioned and supported within the end of conduit 36 bymeans of a plurality of exterior guides and holding members 3? that arespaced around the outside of conduit 36. The internal downstream end ofthe damper member 38 has a central open portion 40 within an inwardlyprojecting flange section 41 which in turn connects with and engages acompression spring 42 which holds the damper member in a normally openposition for low flow rates. The opposing downstream end of thecompress-ion spring 42 is is turn held within the central portion of theair inlet conduit 36 by one or more transverse supporting rib members43. The transverse members 43 are arranged with their edges toward thedirection of gas flow such that air flow may be passed with leasthindrance to the aspirator and become mixed with the exhaust gas flowprior to entering a suitable gas converter means. In other words, as setforth in connection with the other embodiments, the present unit is foruse in combination with a venturi-form aspirator means which willprovide suction and cause the intermixing of secondary air with the flowfrom an exhaust engine to effect a mixed stream introduction into asuitable catalytic or thermal conversion unit, as indicated in FIGURE 3of the drawing.

In the operation of the present embodiment, there will be secondary airintake between the upstream ends of the air inlet conduit 36 and thedamper member 38, with an annular peripheral flow carrying around theexterior wall of the damper member 38, as well as some percentage ofsecondary air flow substantially axially through the cent-er of thehollow damper member 38 and the upstream opening 40. However, as theexhaust gas flow rate increases and the aspiration causes a greatersuction and differential pressure force against the upstream side of themovable damper member 38 there will be a corresponding increase of thepressure of damper member 38 against the compression spring 42 untilsuch time as the damper member effects a closure against the seatingsection 37 at the end of the conduit 36. At this point, the onlysecondary air flow will be that which is drawn through the centralopening 40 from the interior of the damper member 38. Generally, theoperation of the present embodiment will be similar to that of FIGURE 6providing a throttling type of operation, for usual designs andconstructions of the damper member and selection of compression springs,whereby the operation is substantially in accordance with curve D ofFIGURE 2.

From the descriptions of the foregoing embodiments, it should be notedthat variations may be made in providing a movable damper means to atleast partially block the secondary air flow through a conduitresponsive to exhaust gas flow rate or engine speed by reason of the useof a venturi-form aspirator. Further, it may be noted that by a properchoice of balancing means there may be throttling action or asubstantially snap action type of control in effecting the blockage toair flow at predetermined engine speeds or gas flow rates and that suchbalancing means may be either counterweight means or spring means. Inall embodiments, however, it is within the scope of the presentinvention to provide some partially open area such that secondary airflow is not blocked entirely, even at high speeds or flow rates; suchopen area being around the damper or through an opening or openings inthe damper itself or in the conduit downstream of the damper.

We claim as our invention:

1. In combination with an engine exhaust gas converter and aventuri-form aspirating nozzle which provides exhaust gas and secondaryair flow to said converter, an improved secondary air inlet regulatormeans comprising, in combination, a secondary air inlet formed from anopen-ended conduit connected with the throat portion of saidventuri-form aspirating nozzle, a damper member having a rotatablymounted plate positioned internally within said air inlet conduit on ashaft member mounted thereon, said plate being sized smaller than saidinlet air conduit to provide space therebetween, said plate furtherhaving a curved airfoil edge extending parallel to said shaft member, aload means comprising a spiral wound coiled spring member connected toat least one end portion of said shaft member and having its other endfixedly connected with said air inlet conduit and positioned to hold therotatably mounted plate open in said air inlet conduit at low flow ratestherethrough, said load means being balanced against air flow throughthe conduit to effect movement of the damper and partial blocking of theair inlet, and said damper member acting responsive to and throttlingsaid air flow thereby to correspond substantially to the stoichiometricamount of secondary air needed for eflicient oxidation of the exhaustgases at all engine speeds.

2. In combination with an engine exhaust gas converter and aventuri-t'orm aspirating nozzle which provides exhaust gas and secondaryair flow to said converter, an

improved secondary air inlet regulator means comprising, in combination,a secondary air inlet formed from an open-ended conduit connected withthe throat portion of said venturi-form aspirating nozzle, a dampermember comprising a rotatably mounted plate positioned entirely withinsaid air inlet conduit on a shaft member mounted therein, said shaftmember having at least one end portion extending through the wall ofsaid air inlet conduit, said plate sized smaller than said inlet conduitto provide space therebetween, said plate further having a curvedairfoil edge extending parallel to said shaft member, load meansconnected to the end of said shaft member which extends through thewall, and said load means being positioned to hold the rotatably mountedplate open at low flow rates through said inlet conduit and balancedagainst air flow through the conduit to effect movement of the damperand partial blocking of the air inlet, and said damper member acting toresponsive to and throttling said air flow thereby to correspondsubstantially to the stoichiometric amount of secondary air needed forefficient oxidation of the exhaust gases at all engine speeds.

3. In combination with an engine exhaust gas converter and aventuri-form aspirating nozzle which provides exhaust gas and secondaryair flow to said converter, an improved secondary air inlet regulatormeans comprising in combination, a secondary air inlet formed from anopenended conduit connective with the throat portion of saidventuri-form aspirating nozzle, a movable hollow plugform damper memberpositioned within the end portion of said conduit, peripheral seat meanswithin the interior of said conduit adapted to engage a peripheralportion of said damper member, whereby air flow around said dampermember may be blocked, guide means holding said damper member in arestricted aligned movement within and along said conduit portion,compression spring means having one end in engagement with said dampermember and the other end in engagement with support means from theinterior of said conduit and holding said damper member in a normallyunseated position therein, and air passageway means extending throughsaid damper member and said seat means in said conduit whereby limitedair fiow may continue uninterrupted through said conduit when saiddamper member engages said seat, said compression spring means balancedagainst air flow through the conduit to effect movement of said damperwith respect to its seat and partial blocking of the air flow, and saiddamper member acting responsive to and throttling said air flow therebyto correspond substantially to the stoichiometric amount of secondaryair needed for efficient oxidation of the exhaust gases at all enginespeeds.

References Cited by the Examiner UNITED STATES PATENTS 1,781,366 11/1930Campula 137-513.3 2,111,611 3/1938 Brenner 137520 2,232,981 2/1941Swanson 137520 X 2,649,685 8/1953 Cohen -30 2,716,398 8/1955 McMullen137517 X 3,086,353 4/1963 Ridgway 6030 FOREIGN PATENTS 839,419 4/1939France.

SAMUEL LEVINE, Primary Examiner.

EDGAR W. GEOGHEGAN, Exainmer.

1. IN COMBINATION WITH AN ENGINE EXHAUST GAS CONVERTER AND A VENTURI-FORM ASPIRATING NOZZLE WHICH PROVIDES EXHAUST GAS AND SECONDARY AIR FLOW TO SAID CONVERTER, AN IM- 